1. Field of the Invention
The present invention relates to a liquid crystal (LCD) display device for improving color washout effect, and more particularly, to an LCD device for improving color washout effect, caused by a side viewing angle, by modulating sub-pixel voltages through driving signals of scan lines.
2. Description of the Prior Art
Liquid Crystal Display (LCD) devices have many advantages, such as compact size, low power consumption, and low radiation. Therefore, the LCD devices have been widely applied to a mass of digital products, such as a laptop, a desktop and a personal digital assistance (PDA), and gradually replaced conventional Cathode Ray Tube (CRT) televisions to become the mainstream of consumer TV applications.
Compared with the conventional CRT device, the LCD devices tend to have brightness variation and contrast variation due to all kinds of viewing angle, and even have gray level inversion when the viewing angle is wide. Thus, a bunch of technologies, such as Multi-domain Vertical Alignment (MVA), In-Plane Switching (IPS), and etc, have been developed in industry to improve the LCD viewing angle problems. However, there still exists color washout effect and Gamma curve offset in the MVA LCD devices when people watch the screen from a large viewing angle.
One of driving approaches in the prior art, for solving the color washout effect, is dividing each pixels of the LCD into two sub-pixels. Each of sub-pixels is individually controlled by a Thin Film Transistor (TFT). Thus, by inputting two driving voltages with a subtle difference to two sub-pixels, liquid crystals of the two sub-pixels would have different inclined angles, and thereby improve the washout effect caused by a large viewing angle.
Further, as disclosed in US patent publication No. US20040001167A1, entitled “Liquid Crystal Display Device”, an LCD device connects a storage capacitor of each sub-pixel to an external signal. After the TFT of each sub-pixel turns off, voltages on a counter electrode of the storage capacitors are disturbed by the external signals to diverge driving voltages of two sub-pixels, so as to improve the washout effect.
However, the aforementioned doings need not only an extra circuit for generating modulation signals of the storage capacitors, but extra layouts on the LCD panel for transmitting modulation signals of the storage capacitors. As a result, the aperture ratio of the LCD is decreased.